Horizon Pharma and Mallinckrodt, the Pharmaceuticals Business of Covidien, Enter Into Co-Promotion Agreement for DUEXIS® in the United States

Mallinckrodt to Begin Promoting DUEXIS in August

DEERFIELD, Ill.,June 18, 2012/PRNewswire/ — Horizon Pharma, Inc.(NASDAQ: HZNP) andMallinckrodt LLCthe Pharmaceuticals business ofCovidien(NYSE: COV), announced today that they have entered into a U.S. co-promotion agreement for DUEXIS® (ibuprofen and famotidine), which is indicated for the relief of signs and symptoms of rheumatoid arthritis and osteoarthritis and to decrease the risk of developing upper gastrointestinal ulcers. “This collaboration withMallinckrodtwill expand our reach and frequency against key primary care physicians who treat patients with osteoarthritis and rheumatoid arthritis,” saidTimothy P. Walbert, chairman, president and chief executive officer of Horizon Pharma. “The Horizon sales force has performed well in the initial phase of the DUEXIS launch. As part of our continued commercial strategy, we believe the substantial promotional efforts ofMallinckrodt, along with increasing our own sales force with an additional 80 sales representatives will enable us to achieve critical mass in driving DUEXIS revenue.” Under the terms of the agreement, Horizon grantedMallinckrodtthe right to co-promote DUEXIS inthe United StatesthroughDecember 31, 2014with the potential to renew for additional periods. Horizon andMallinckrodthave agreed thatMallinckrodtwill promote to targeted physicians and is entitled to receive performance-based compensation. The Mallinckrodt sales force is expected to begin promoting DUEXIS to physicians in August 2012. Horizon will continue to record all revenues for DUEXIS and will remain responsible for DUEXIS manufacturing, supply and regulatory activities. “DUEXIS is a perfect complement to our existing portfolio of pain products,” saidMark Trudeau, president, pharmaceuticals, Covidien. “We look forward to using our experience and relationships to expand adoption of DUEXIS by primary care physicians.” About DUEXIS DUEXIS, a proprietary single-tablet combination of the NSAID ibuprofen and the histamine H2-receptor antagonist famotidine, is indicated for the relief of signs and symptoms of rheumatoid arthritis and osteoarthritis and to decrease the risk of developing upper gastrointestinal ulcers, which in the clinical trials was defined as a gastric and/or duodenal ulcer, in patients who are taking ibuprofen for those indications. The clinical trials primarily enrolled patients less than 65 years of age without a prior history of gastrointestinal ulcer. Controlled trials do not extend beyond 6 months. For more information, please visit www.DUEXIS.com. Important Safety Information About DUEXIS DUEXIS is not right for everyone. People who have had asthma, hives, or an allergic reaction to aspirin or other NSAIDs should not take DUEXIS. Women in the late stages of pregnancy should not take DUEXIS. People who have had allergic reactions to medications like famotidine (histamine H2‐receptor antagonists) should not take DUEXIS. Tell your health care provider right away if you have signs of active bleeding (persistent and unexplained) while you are taking DUEXIS. NSAID‐containing medications like DUEXIS can cause high blood pressure or make existing high blood pressure worse, either of which can increase the chance of a heart attack or stroke. Your health care provider should check your blood pressure while you are taking DUEXIS. Before you start taking DUEXIS, tell your health care provider if you have heart problems, kidney problems, or liver problems, or if you are taking medications for high blood pressure. DUEXIS can increase the chance of potentially significant liver injury and/or kidney injury, which may be fatal. Stop taking DUEXIS immediately and contact your health care provider if you experience any signs and/or symptoms of liver or kidney injury. Serious allergic reactions, including skin reactions, can happen without warning and can be life threatening. Stop taking DUEXIS and consult your doctor immediately if you get a skin rash or if you start to have problems breathing or swallowing, or if you develop swelling of your face or throat. The most common side effects of DUEXIS include nausea, diarrhea, constipation, upper abdominal pain, and headache. Please see Medication Guide and full Prescribing Information. About Horizon Pharma Horizon Pharma, Inc.is a biopharmaceutical company that is developing and commercializing innovative medicines to target unmet therapeutic needs in arthritis, pain and inflammatory diseases. For more information, please visit www.horizonpharma.com. Forward-Looking Statements This press release contains forward-looking statements, including statements regarding future activities conducted under the co-promotion agreement, the potential benefits of the co-promotion agreement, including benefits to the commercial launch of DUEXIS and increasing revenues from DUEXIS sales, the timing ofMallinckrodt’s promotional efforts and Horizon’s plans to expand its sales force. These forward-looking statements are based on management’s expectations and assumptions as of the date of this press release, and actual results may differ materially from those in these forward-looking statements as a result of various factors. These factors include each party’s performance of its respective obligations under the co-promotion agreement, the ability of each party’s sales force to successfully promote and commercialize DUEXIS, the parties’ ability to successfully collaborate with one another under the co-promotion agreement regarding sales and marketing plans and strategy, the parties’ ability to terminate the co-promotion agreement, existing competition for DUEXIS in the U.S., the extent to which healthcare professionals will prescribe DUEXIS and the extent to which such prescriptions result in actual sales and other factors described in Horizon’s filings with theUnited States Securities and Exchange Commission, including those factors discussed under the caption “Risk Factors” in those filings. Forward-looking statements speak only as of the date of this press release, and Horizon undertakes no obligation to update or revise these statements, except as may be required by law.